Albert P. Williams

The diffusion of magnetic resonance imaging scanners in a changing U.S. health care environment

Technological aspects and early clinical experiences are arousing great enthusiasm over magnetic resonance imaging (MRI). However, influences such as regulation, reimbursement, and increasing competition also are playing important roles in determining the diffusion of this new technology. Of these considerations, competition among providers seems the most important. Competition related to MRI is manifested as direct competition over MRI services, using MRI to improve a providers strategic position and competition among specialties. In making decisions concerning MRI acquisition and operation, providers are drawing upon their experiences with computed tomography (CT) to help them determine when would be the best time for acquisition, how to decide whether acquisition is appropriate, and how best to acquire, operate, and market the technology.

Medical School Admission and Residence of Applicants: Empirical Bayes Estimates of Logit Coffficients:

Using data on all applicants to U.S. medical schools in 1975, we analyzed how an applicant’s characteristics affect the probability of his admission to medical school. Specifically, separate logit regressions for minority and majority applicants are performed to estimate this probability as a function of the applicant’s academic attributes (admission test scores, grade point averages, etc.) and of his non-academic attributes (state of residence, age, etc.). The coefficients of the state of residence dummy variables in the logit equation are estimated by discriminant analysis and then modified by empirical Bayes methods to give more accurate estimates of the state of residence effects. These modified estimates show that state of residence has a much larger effect for majority applicants than for minority applicants. An exploratory regression analysis indicates that legal residents of states with high ratios of medical school places to population are more likely to be admitted to a medical school.